If someone you barely know hands you a book and says, "Here, I really think you’ll like this book". Is the unspoken expectation to give the book back after reading it, or to keep the book it’s yours now?

I've had several instances in my life where this scenario has occured. Sometimes I have held on to the book for so long because I'm reading too many other books, and it simply gets forgotten about. By the time I get around to it months or years have gone by and the giver of the book has never asked about it. Other instances I have read the book and gave it back only to be told that it was mine to be given to. And yet, other instances that I've given it back, and the giver said thanks.

What say you fine bibliophobes of Reddit?